Q.1 Which of the following is the most commonly used local anesthetic in dentistry?
Lidocaine
Bupivacaine
Procaine
Cocaine
Explanation - Lidocaine is the most widely used dental anesthetic due to its rapid onset, moderate duration, and safety profile.
Correct answer is: Lidocaine
Q.2 What is the primary mechanism of action of local anesthetics?
Inhibition of dopamine release
Blockade of sodium channels
Enhancement of potassium channels
Stimulation of GABA receptors
Explanation - Local anesthetics block voltage-gated sodium channels in nerve membranes, preventing depolarization and conduction of nerve impulses.
Correct answer is: Blockade of sodium channels
Q.3 Epinephrine is commonly added to local anesthetics because it:
Increases absorption
Decreases duration
Reduces systemic toxicity
Causes vasodilation
Explanation - Epinephrine causes vasoconstriction, reducing systemic absorption, prolonging anesthetic duration, and lowering toxicity risk.
Correct answer is: Reduces systemic toxicity
Q.4 Which local anesthetic is known for its long duration of action and is often used for surgical procedures?
Lidocaine
Bupivacaine
Procaine
Articaine
Explanation - Bupivacaine has a longer duration of action compared to lidocaine and is preferred for lengthy dental and surgical procedures.
Correct answer is: Bupivacaine
Q.5 Which local anesthetic is an ester type?
Lidocaine
Mepivacaine
Procaine
Bupivacaine
Explanation - Procaine is an ester-type anesthetic, while most commonly used modern dental anesthetics are amides.
Correct answer is: Procaine
Q.6 Which enzyme metabolizes ester local anesthetics?
Plasma cholinesterase
Cytochrome P450
Monoamine oxidase
Aldehyde dehydrogenase
Explanation - Ester anesthetics are metabolized in the plasma by pseudocholinesterase, unlike amides which are metabolized in the liver.
Correct answer is: Plasma cholinesterase
Q.7 What is the approximate pKa of lidocaine?
5.5
7.9
9.0
11.0
Explanation - The pKa of lidocaine is around 7.9, which influences its onset of action in tissue environments.
Correct answer is: 7.9
Q.8 What is the maximum recommended dose of lidocaine with epinephrine for an average adult?
100 mg
200 mg
300 mg
500 mg
Explanation - With epinephrine, the maximum safe dose of lidocaine is approximately 7 mg/kg, up to 500 mg in adults.
Correct answer is: 500 mg
Q.9 Which local anesthetic is most associated with methemoglobinemia?
Articaine
Prilocaine
Mepivacaine
Ropivacaine
Explanation - Prilocaine can lead to methemoglobinemia due to its metabolite o-toluidine.
Correct answer is: Prilocaine
Q.10 What is the onset time of lidocaine when used in dental anesthesia?
1–2 minutes
5–10 minutes
15–20 minutes
30 minutes
Explanation - Lidocaine has a rapid onset, typically within 1–2 minutes when used in dentistry.
Correct answer is: 1–2 minutes
Q.11 Which of the following is a potential adverse effect of intravascular injection of local anesthetics?
Bradycardia
Seizures
Diarrhea
Cough
Explanation - Accidental intravascular injection can cause CNS toxicity, leading to seizures and cardiovascular complications.
Correct answer is: Seizures
Q.12 Which factor most influences the potency of a local anesthetic?
Lipid solubility
Protein binding
pKa
Plasma protein levels
Explanation - Greater lipid solubility increases membrane penetration, enhancing the potency of local anesthetics.
Correct answer is: Lipid solubility
Q.13 Which factor determines the duration of action of a local anesthetic?
Protein binding
Lipid solubility
pH of tissue
Volume of injection
Explanation - Local anesthetics with higher protein binding remain longer at the receptor site, prolonging duration of action.
Correct answer is: Protein binding
Q.14 Articaine differs from other amide local anesthetics because it:
Has an ester group
Is metabolized by cholinesterase
Has no amide bond
Is ineffective in dentistry
Explanation - Articaine has both an amide linkage and an ester side chain, allowing partial metabolism in plasma.
Correct answer is: Has an ester group
Q.15 Why is mepivacaine sometimes preferred in pediatric dentistry?
It causes less vasodilation
It is more potent
It has longer duration
It is metabolized faster
Explanation - Mepivacaine produces minimal vasodilation, making it useful without epinephrine in children and patients with contraindications.
Correct answer is: It causes less vasodilation
Q.16 Which anesthetic has the shortest duration of action?
Procaine
Lidocaine
Bupivacaine
Prilocaine
Explanation - Procaine is short-acting and rarely used in dentistry today.
Correct answer is: Procaine
Q.17 Which systemic condition is a contraindication for vasoconstrictor use in dental anesthesia?
Hypertension
Asthma
Diabetes
Gastroenteritis
Explanation - Vasoconstrictors like epinephrine can exacerbate hypertension and cardiac conditions.
Correct answer is: Hypertension
Q.18 Which local anesthetic is least likely to cause allergic reactions?
Procaine
Bupivacaine
Lidocaine
Cocaine
Explanation - Amides like lidocaine have a very low incidence of allergic reactions compared to esters.
Correct answer is: Lidocaine
Q.19 Why is sodium bicarbonate sometimes added to local anesthetics?
To decrease potency
To increase ionized form
To speed onset
To reduce protein binding
Explanation - Sodium bicarbonate raises pH, increasing the non-ionized fraction of anesthetic and speeding onset.
Correct answer is: To speed onset
Q.20 Which local anesthetic is contraindicated in patients with severe liver disease?
Lidocaine
Prilocaine
Bupivacaine
Procaine
Explanation - Amide anesthetics like lidocaine are metabolized in the liver, making them unsuitable in severe hepatic impairment.
Correct answer is: Lidocaine
Q.21 The inferior alveolar nerve block anesthetizes all except:
Lower molars
Lower incisors
Tongue anterior 2/3
Buccal gingiva of molars
Explanation - The long buccal nerve supplies buccal gingiva of molars, not anesthetized by the inferior alveolar block.
Correct answer is: Buccal gingiva of molars
Q.22 Tachycardia after dental local anesthesia is most likely due to:
High dose of lidocaine
Epinephrine absorption
CNS toxicity
Hypersensitivity reaction
Explanation - Systemic absorption of epinephrine can cause tachycardia and palpitations.
Correct answer is: Epinephrine absorption
Q.23 Which local anesthetic is considered safest in pregnancy (Category B)?
Lidocaine
Bupivacaine
Prilocaine
Mepivacaine
Explanation - Lidocaine is FDA Category B and is considered safe for use in pregnant women.
Correct answer is: Lidocaine
Q.24 Which property is most important for rapid onset of action?
Low pKa
High lipid solubility
High protein binding
Strong vasoconstrictor effect
Explanation - A lower pKa increases the proportion of non-ionized drug at physiological pH, speeding onset.
Correct answer is: Low pKa
Q.25 Local anesthetics are less effective in infected tissues because:
Low pH reduces non-ionized form
Drug binds to proteins
Blood flow decreases
Nerve endings are destroyed
Explanation - Infected tissues have acidic pH, reducing the non-ionized fraction of anesthetic, slowing penetration and effectiveness.
Correct answer is: Low pH reduces non-ionized form